[OMPI users] MPI_Allreduce()

[Brock Palen]

I have always been told that calls like MPI_Barrior() MPI_Allreduce()  
and MPI_Alltoall() should be avoided.

I understand MPI_Alltoall()  as it goes n*(n-1) sends and thus grows  
very very quickly.  MPI_Barrior() is very latency sensitive and  
generally is not needed in most cases I have seen it used.

But why MPI_Allreduce()?
What other functions should generally be avoided?

Sorry this is kinda off topic for the list :-)

Brock Palen
Center for Advanced Computing
bro...@umich.edu
(734)936-1985